The EVAP control system prevents the emission of fuel vapors. The fuel vapors generated in the fuel tank while driving or idling the engine, pass through the fuel tank pressure control valve and enter the EVAP canister. The fuel vapors are stored in the charcoal element of the EVAP canister. The powertrain control module (PCM) operates the EVAP canister purge valve, allowing the fuel vapors to be drawn into the intake manifold from the EVAP canister. The DTC P0443 diagnostic monitors the EVAP canister purge valve control circuit voltage.

The ignition is ON, or the engine is running.

If a DTC P0440 and P0443 are both set, the most likely cause is an inoperable EVAP canister purge valve. Inspect the EVAP canister purge valve carefully for faulty connections and erratic operation.

If a DTC P0443 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P0443 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0443 appears in the Not Ran Since Code Cleared list, the P0443 diagnostic has not yet run. When the DTC P0443 does not appear in the Not Ran Since Code Cleared list, the P0443 diagnostic has run. If the MIL is NOT ILLUMINATED, and there is no PENDING DTC Status in DTC Information, the P0443 diagnostic has passed. DTCs MUST BE CLEARED in order to view the CURRENT STATUS of the Not Ran Since Code Cleared list. DO NOT FORGET that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for CURRENT or PENDING status, in order to determine the outcome of the diagnostic test involved.

Test the operation of the EVAP canister purge valve. Refer to Evaporative Emission Control System Diagnosis .

An intermittent malfunction may be caused by a fault in the EVAP canister purge valve electrical circuit. Inspect the wiring harness and components for any of the following conditions:

If you duplicate a DTC P0443, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

The numbers below refer to the step numbers in the diagnostic table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step checks whether the condition that caused the DTC P0443 to set still exists.

5. This step checks the EVAP canister purge valve control circuit. The EVAP canister purge valve duty cycle control is disabled by the PCM until the engine has reached a normal operating temperature of at least 80°C (176°F), there is no RPM indicated, and there are no DTCs set. Output controls can be found on the scan tool under Special Functions.

10. This step checks whether the malfunction that caused the DTC P0443 is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool Clear DTC Information function, the DTC P0443 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0443 appears in the Not Ran Since Code Cleared list, the P0443 diagnostic has not yet run. When the DTC P0443 does not appear in the Not Ran Since Code Cleared list, the P0443 diagnostic has run. If the MIL is NOT ILLUMINATED and there is no PENDING DTC Status in DTC Information, the P0443 diagnostic has passed. DTCs MUST BE CLEARED in order to view the CURRENT STATUS of the Not Ran Since Code Cleared list. DO NOT FORGET that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for CURRENT or PENDING status, in order to determine the outcome of the diagnostic test involved.